Wind is a powerful renewable energy source that civilizations have harnessed to varying degrees for several thousand years. Historians accredit ancient Mesopotamia and Egypt as giving rise to sail-based propulsion systems for boats, while most accounts accredit ancient Persia as having developed and implemented windmills in 500 to 900 AD. In around 1390, the Dutch began to refine the windmill, eventually implementing thousands for various applications such as irrigation, land drainage, grain-grinding, saw-milling and the processing of commodities.
With the current awareness of global warming and the human impact upon the environment, there is an increasing shift towards greener, ecologically-friendly technologies. While fossil fuel-fired and nuclear power plants have been standard methods of power generation for the last century, alternative methods for power generation, particularly from renewable energy sources such as the sun and wind have been attracting increasing attention from industry, governments and the general public.
Modern windmills for power generation, or wind turbines, are growing in popularity, with wind farms being established in many countries around the world. Modern windmills come in a variety of sizes and configurations, but many people associate them with the large horizontal wind turbines used for large scale energy generation. These large turbines can stand as tall as 90 meters, with generally three equidistantly spaced blades measuring upwards of 30 meters each.
At the same time, there is growing interest for smaller turbine units that are 3 kW to 99 kW that are better suited to farm and residential application. Unfortunately, these smaller units are subject to less than optimal wind characteristics as they are generally located on lower towers for aesthetic, economic, and practical reasons. As such, there is a need for smaller turbine units having wind capturing characteristics that are suited for the conditions under which these smaller turbine units are operated.